Pituitary tumors were removed transsphenoidally in 32 patients with acromegaly. Ten patients had high prolactin (PL) levels as well as elevated growth hormone (GH) levels. In 24 patients, GH levels were lowered to 5 ng/mL or less and remained low. The PL level was reduced to normal in eight patients. Of three patients with postoperative GH levels of 6 to 10 ng/mL, one patient remains in this range but two have relapsed. Five patients showed only a partial lowering in GH level. Pituitary irradiation lowered the level further. Hypopituitarism developed in four patients. Permanent diabetes insipidus occurred in one patient and meningitis developed in another. They subsequently recovered. There were no deaths. Abnormal GH responses to hyperglycemia, hypoglycemia, and levodopa returned to normal following surgery. Transsphenoidal tumor removal appears to be an effective treatment for acromegaly.